How are p type and n type semiconductors formed

how are p type and n type semiconductors formed

Difference between P-type Semiconductor and N-type Semiconductor

FORMATION OF P-TYPE SEMI CONDUCTOR A P - type semiconductor is formed when a small amount of trivalent impurity is added to pure Germenium or silicon atom crystal. The addition of . Apr 04,  · N-type semiconductors are created by doping an intrinsic semiconductor with donor impurities. A common dopant for n-type silicon is phosphorus. The term p-type refers to the positive charge of the hole. In p-type semiconductors, holes are the majority carriers and electrons are the minority carriers.

Semiconductive materials do not conduct current well and are of limited value in their intrinsic state. This is because of the limited number of free electrons in the conduction band and holes in the valence band. Intrinsic silicon or germanium must be modified by increasing the number of free electrons or holes to increase its conductivity and make it useful in electronic devices. This is done by adding impurities to the intrinsic material. Two types of extrinsic impure semiconductive materials, n-type and p-type, are the key building blocks for most types of electronic devices.

Since semiconductors are generally poor conductors, their conductivity can be drastically increased by the controlled addition of impurities to the intrinsic pure P. This process, called doping, increases the number of current carriers electrons or holes. Cormed two categories of impurities are n-type and p-type.

To how to make a bass box the number of conduction-band electrons in intrinsic silicon, pentavalent impurity atoms are added.

These are atoms with five valence electrons such as arsenic Asphosphorus Pbismuth Biand antimony Sb. As illustrated in Semiconduxtors Figure, each pentavalent atom antimony, in this case forms covalent bonds with four adjacent silicon atoms. This extra electron becomes a conduction electron because it is not involved in bonding. Because the sekiconductors atom gives up an electron, it is often called a donor atom. The number of conduction electrons can be carefully controlled by the number of impurity atoms added to the silicon.

A conduction electron created by this doping process does not leave a hole in the valence band because it is in excess of the number required to fill the valence band. Fig: Pentavalent impurity atom in a andd crystal structure.

An antimony Sb impurity atom is shown in the center. The extra electron from the Sb atom becomes a free electron. Majority and Minority Carriers Since most of the current carriers are electrons, silicon or germanium doped with pentavalent atoms is an n-type semiconductor the n stands for the negative charge on an electron. The electrons are called the majority carriers in n-type material. Although the majority of current carriers in n-type material are electrons, there are also a few holes that are created when electron-hole pairs are thermally generated.

These holes formes not produced by the addition of the pentavalent impurity atoms. Holes in an n-type material are called minority carriers. To increase how to stop scratching poison ivy number of holes in intrinsic silicon, trivalent impurity atoms are added.

These are atoms with three valence electrons such as boron Bindium Inand gallium Ga. As illustrated in Below Figure, each trivalent atom boron, in this case forms covalent bonds with four adjacent silicon atoms. Because the trivalent atom can take an electron, it is often referred to as an acceptor atom.

The number of holes can be carefully controlled by the number of trivalent impurity atoms added to the silicon. A hole created rormed this doping process is not accompanied by a conduction free electron. Fig: Trivalent impurity atom in a silicon crystal structure. A boron B impurity atom is shown in the center. Majority and Minority Carriers Since most of how to view ntuser dat current carriers are holes, silicon or germanium doped with trivalent atoms is called a p-type semiconductor.

The holes are the majority carriers in p-type material. Although the majority of current carriers in p-type material are holes, there are also a few how are p type and n type semiconductors formed electrons that are created when electron-hole pairs are thermally generated. These conduction-band electrons are not produced by the addition of the trivalent impurity atoms.

Conduction-band electrons in p-type fprmed are the minority carriers. Save my name, email, and website in this browser for the next time I comment.

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Apr 01,  · Based on the type of doping material incorporated, semiconductor crystals are classified into two types particularly n-type semiconductors and p-type semiconductors. Group –V elements such as phosphorus, antimony and arsenic are usually classified as N-type impurities. These elements have five valence electrons. Oct 11,  · N-type Semiconductor: When the group V element is added to the intrinsic or pure semiconductor (silicon or Germanium), the resulted product is said to be an n-type semiconductors. The group V elements are phosphorus, arsenic, antimony and this elements have five valence electrons. A p-type semiconductor material is formed by the addition of group III elements or we can say trivalent impurity to a pure (intrinsic) semiconductor. On the contrary, the n-type semiconductor material is formed by the addition of group V elements i.e., a pentavalent impurity to a .

Both p-type and n-type semiconductor is the classification of extrinsic semiconductors. The major factor that generates a difference between p-type and n-type semiconductor lies in their doping material. A p-type semiconductor material is formed by the addition of group III elements or we can say trivalent impurity to a pure intrinsic semiconductor. On the contrary, the n-type semiconductor material is formed by the addition of group V elements i.

Some other factors also exist that generates major differences between the two. We will discuss these differences in detail but before proceeding towards that have a look at the contents that are to be discussed under this article. When a pure or intrinsic semiconductor is doped with group III elements of periodic table like boron, gallium, aluminium etc.

These are called so because doping these elements will lead to the presence of an extra hole in the valence shell of the atom. Let us have a look at the figure shown below that represents doping of aluminium to a pure silicon material:. As we know that an aluminium atom contains 3 electrons at its valence shell.

Also, silicon contains total of 4 electrons at its valence shell. So, 3 valence electrons of aluminium atom make covalent bonds with 3 electrons of silicon. However, in this case, a vacancy of an electron or a hole appears. The movement of this hole is mainly responsible for the conduction in the p-type semiconductor to take place. Hence, in this case, charge carriers are holes rather than electrons. Here, we can see that the Fermi level is present near the valence band. As it is clear from the above figure that there exists a very small energy difference between valence band and the acceptor energy level.

Thus, electrons easily drift to acceptor energy level creating a vacancy of electrons. Hence, producing holes in the valence band. N-type extrinsic semiconductors are formed when group V elements like phosphorus, antimony, bismuth etc. These are called so because doping these elements will cause the presence of an additional electron in the valence shell of the atom. The figure below represents the doping of phosphorus element into a pure silicon material:.

We already know that phosphorus consists of 5 electrons at its valence shell. When it is doped with pure silicon having 4 electrons at the valence shell then it forms 4 covalent bonds. This leads to the presence of an unbounded electron that is held free to move into the conduction band. This electron is known as a free electron and its movement raises the conductivity of the material. Here, from the figure, it is clear that the existence of the Fermi level is near the conduction band.

We can see that the small energy difference exists between donor energy level and the conduction band. So, less energy is needed by the electrons to reach the conduction band. So, from the above discussion, we can conclude that a p-type semiconductor is abbreviated so because these are positive semiconductors due to presence of extra holes. Whereas, n-type semiconductors are termed as negative semiconductors because of the presence of extra electrons.

Your email address will not be published. Skip to content. As against, an n-type semiconductor is formed when group V elements are doped to an intrinsic semiconductor. As elements like boron, gallium, indium etc. On the contrary, elements like arsenic, antimony, bismuth etc. Another factor that generates a key difference between p-type and n-type semiconductor is that in case of p-type semiconductor holes are the majority carriers.

While in case of n-type semiconductor electrons act as majority carriers. The minority carriers in case of the p-type semiconductor are electrons whereas in that of n-type semiconductor these are holes. As we know that the conductivity of the device depends on the majority carriers. Thus in the p-type semiconductor, holes are responsible for current conduction. On the contrary, in case of an n-type semiconductor, electrons are responsible for current conduction.

The fermi-level in case of p-type semiconductor appears closer to valence band than that of the conduction band. As against, the Fermi level in case of n-type semiconductor exists near the conduction band. The concentration of holes is more than electrons in case of p-type semiconductor material. While in n-type semiconductors the concentration of electrons is greater than holes. Leave a Comment Cancel Reply Your email address will not be published.

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